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Karyotypes of O . meinerti (a), O . chelifer (b), A . horridus (c), and A . altisquamis (d). CMA 3 -positive bands (green bands) are shown on the 15th chromosome pair of O . meinerti and on the 11th chromosome pair of O . chelifer . rDNA 45S genes (red bands) localized by FISH are shown on the 10th chromosome pair of A . horridus and on the ninth chromosome pair of A . altisquamis . Bars ϭ 5 m. (Online Þgure in color.)
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Odontomachus (Latreille) and Anochetus (Mayr) (Hymenoptera: Formicidae: Ponerinae) are closely related pantropical genera of ponerine ants that share morphological and behavioral characteristics. A comparative study was carried out using conventional Giemsa staining, fluorochrome staining, and fluorescent in situ hybridization. Karyotypes revealed...
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Citations
... In his study of Odontomachus, Brown (1976) mentioned that the genus apparently arose from a primitive Anochetus species, based on morphological characters of the posterior vertex and the apophyseal line, present on the head of Odontomachus but absent in Anochetus. Data from karyotypes (Santos et al., 2010) and adductor muscle morphology (Gronenberg & Ehmer, 1996) support this scenario, with Anochetus possessing ancestral states of both characters (posterior vertex and the apophyseal line). Other aspects of morphology have apparently evolved more rapidly in Anochetus than in Odontomachus, including body size, reduction in eye size and reduced pigmentation associated with cryptobiosis in A. myops, A. talpa and A. minans. ...
We present a phylogeny of the trap‐jaw ant genera Anochetus and Odontomachus with dense taxon sampling representing all biogeographical regions and all species groups for both genera. Four nuclear protein‐coding genes (Long‐wavelength rhodopsin, Topoisomerase I, Wingless and Rudimentary) and one mitochondrial gene (cytochrome oxidase I) were sequenced for 221 individuals of Anochetus (44 species) and Odontomachus (38 species). Analyses using Bayesian and maximum‐likelihood criteria recovered essentially the same phylogenetic relationships, including strongly supported reciprocal monophyly of both genera. The analyses recovered nine of the 12 species groups previously proposed for Odontomachus and nine of the 22 species groups previously proposed for Anochetus. Based on these results, species groups are redefined. Anochetus contained an additional new, previously unrecognized group defined here as the hohenbergiae group. Divergence‐time analyses estimated the clade composed of Odontomachus + Anochetus arose during the early Paleocene, with Odontomachus and Anochetus diverging during the Eocene. Biogeographic analyses suggest that the most recent common ancestor (MRCA) of Odontomachus and Anochetus occupied either the Neotropical or Afrotropical region during the late Cretaceous and that the two genera radiated during the early Paleocene. The ancestor of Odontomachus originated in the Neotropical or Afrotropical regions, giving rise to lineages that radiated during the late Eocene, and the ancestor of Anochetus originated in the Neotropical region, giving rise to lineages that radiated during the early Eocene.
... Since then, the number of studies mapping these genes has increased (Mariano et al., 2008;Santos et al., 2016;Micolino et al., 2019a;Teixeira et al., 2020) and other repetitive sequences, such as telomeres (Meyne et al., 1995;Pereira et al., 2018;Micolino et al., 2020;Castro et al., 2020), satellite DNA (Lorite et al., 2004;Huang et al., 2016), 5S ribosomal genes , and microsatellites (Barros et al., 2018;Micolino et al., 2019b), have been mapped in the chromosomes using the FISH technique. To date, molecular cytogenetic studies on rDNA genes in ants have improved understanding of chromosomal evolution and phylogeny and provided taxonomic resolutions for different ant groups (Hirai et al., 1994(Hirai et al., , 1996Santos et al., 2010Santos et al., , 2016. ...
... Gnamptogenys tortuolosa is an exception, with rDNA clusters occurring over the entire long arm (this study). In the genus Anochetus, the chromosome number ranges from 2n = 30 to 46, and a single pericentromeric rDNA site has been observed (Santos et al., 2010). ...
The major rDNA genes are composed of tandem repeats and are part of the nucleolus organizing regions (NORs). They are highly conserved and therefore useful in understanding the evolutionary patterns of chromosomal locations. The evolutionary dynamics of the karyotype may affect the organization of rDNA genes within chromosomes. In this study, we physically mapped 18S rDNA genes in 13 Neotropical ant species from four subfamilies using fluorescence in situ hybridization. Furthermore, a survey of published rDNA cytogenetic data for 50 additional species was performed, which allowed us to detect the evolutionary patterns of these genes in ant chromosomes. Species from the Neotropical, Palearctic, and Australian regions, comprising a total of 63 species from 19 genera within six subfamilies, were analyzed. Most of the species (48 out of 63) had rDNA genes restricted to a single chromosome pair in their intrachromosomal regions. The position of rDNA genes within the chromosomes appears to hinder their dispersal throughout the genome, as translocations and ectopic recombination are uncommon in intrachromosomal regions because they can generate meiotic abnormalities. Therefore, rDNA genes restricted to a single chromosome pair seem to be a plesiomorphic feature in ants, while multiple rDNA sites, observed in distinct subfamilies, may have independent origins in different genera.
... Odontomachus haematodus presented 2n=44; 2K=8sm+ 18st+18t ( Fig 2E). The monophyletic genus Odontomachus includes 74 species described (Larabee et al., 2016;Bolton, 2020), with 13 taxa studied cytogenetically (reviewed by Santos et al., 2010;Mariano et al., 2019). The karyotype formula varies among species, specifically, the number of acrocentric chromosomes, due to differential growth of heterochromatin chromosomal evolution of the genus . ...
The Brazilian Atlantic rainforest is an endangered biome and biodiversity hotspot. Ant cytogenetic studies from this biome showed remarkable chromosomal diversity among species, and provided useful insights on phylogeny, chromosomal evolution, and taxonomy. In this study, we karyotyped five ant taxa from the Atlantic rainforest. The karyotypes observed were Pheidole germaini 2n=22, Pheidole sp. flavens group 2n=20, Brachymyrmex admotus 2n=18, Camponotus atriceps 2n=40, and Odontomachus haematodus 2n=44. The data obtained for Pheidole spp. represent the first chromosomal record for the genus in Brazil and provide insights on the chromosomal evolution of P. germaini. Karyotypic information from B. admotus brings the genus back to the cytogenetic scenario after decades of neglect. No karyotype variations were observed among the C. atriceps and O. haematodus from different already studied populations, corroborating their status as good species. This study increased the cytogenetic knowledge of ants from the Brazilian Atlantic rainforest.
... Cytogenetic data are only available for 18 ant species from the Amazon region, mostly (13 species) from French Guiana , Santos et al. 2010, with four species from the state of Pará, Brazil , Santos et al. 2012, and one species from Amapá, Brazil . Until now, only data for T. rogenhoferi, is available for two locations: Pará, Brazil and French Guiana . ...
... Anochetus targionii has 2n = 30 chromosomes (Fig. 1a), which is considered as a modal number according to Santos et al. (2010). Anochetus chromosome numbers range from 2n = 24-46, which represents higher karyotype diversity than that found in Odontomachus (2n = 32-42) (reviewed in Mariano et al. 2019). ...
... Anochetus chromosome numbers range from 2n = 24-46, which represents higher karyotype diversity than that found in Odontomachus (2n = 32-42) (reviewed in Mariano et al. 2019). However, only 12 morphospecies out of 113 valid species of Anochetus have been cytogenetically analyzed: nine from the Indo-Malayan and three from the Neotropics, A. altisquamis Mayr, 1887 (2n = 30), A. horridus Kempf, 1964 (2n = 46), and A. emarginatus (Fabricius, 1804) (2n = 28) (Santos et al. 2010. Since Anochetus diversified earlier than Odontomachus (Larabee et al. 2016, Fernandes 2017), higher karyotypic variation in Anochetus would be expected (Santos et al. 2010). ...
Ants play essential roles in most terrestrial ecosystems and may be considered pests for agriculture and agroforestry. Recent morphological and molecular data have challenged conventional ant phylogeny and the interpretation of karyotypic variations. Existing Neotropical ant cytogenetic data focus on Atlantic rainforest species, and provide evolutionary and taxonomic insight. However, there are data for only 18 Amazonian species. In this study, we describe the karyotypes of 16 ant species belonging to 12 genera and three subfamilies, collected in the Brazilian state of Amapá, and in French Guiana. The karyotypes of six species are described for the first time, including that of the South American genus Allomerus Mayr, 1878. The karyotype of Crematogaster Lund, 1831 is also described for the first time for the New World. For other species, extant data for geographically distinct populations was compared with our own data, e.g. for the leafcutter ants Acromyrmex balzani (Emery, 1890) and Atta sexdens (Linnaeus, 1758). The information obtained for the karyotype of Dolichoderus imitator Emery, 1894 differs from extant data from the Atlantic forest, thereby highlighting the importance of population cytogenetic approaches. This study also emphasizes the need for good chromosome preparations for studying karyotype structure.
... 18S y 5S, que son regiones bastante conservadas evolutivamente e importantes marcadores genéticos para diferentes organismos con el objetivo de proporcionar una mejor comprensión de la evolución cromosómica y filogenética de las especies (Sumner, 2003;Kasahara, 2009). Los datos de citogenética molecular de hormigas neotropicales son extremamente escasos, estando disponibles para Dinoponera lucida , Mycocepurus goeldii , Anochetus horridus, Anochetus altisquamis (Santos et al., 2010), Acromyrmex spp. (Barros, 2010;Barros et al., 2016) y Dinoponera gigantea (Aguiar et al., 2011a). ...
... 36. Santos et al. (2010). 37. Santos et al. (2012). ...
Las primeras descripciones de cromosomas se originaron a finales del siglo xix. El estudio de los cromosomas se ha destacado en diversas disciplinas, no solo porque son esenciales para el mecanismo hereditario, sino también porque permiten inferir en numerosos aspectos de la biología, reproducción, filogenia y evolución de los organismos. Una línea de investigación con el objetivo de ser cada vez más aplicada, la “taxonomía integrativa”, utiliza, además de caracteres morfológicos, una
combinación de disciplinas como la genética molecular, ecología, citogenética, comportamiento y biogeografía, entre otras. A excepción de la subfamilia Martialinae, se puede encontrar información citogenética para especies de todas las subfamilias de hormigas neotropicales. Sin embargo, estas informaciones se distribuyen de manera desigual tanto en los grupos taxonómicos como geográficamente, concentrándose principalmente en algunos estados de Brasil. En este capítulo, se presenta una revisión y una actualización de los conocimientos citogenéticos en hormigas neotropicales, las principales técnicas utilizadas en estudios citogenéticos, así como modelos de análisis para inferir en la evolución del cariotipo en hormigas. También se discute sobre determinados procesos como el modelo reproductivo de himenópteros, la constancia del tamaño del genoma en las hormigas, la ocurrencia de machos diploides y se formula una hipótesis sobre la evolución del cariotipo en la familia Formicidae.
Abstract
The first descriptions of chromosomes originated in the late 19th Century. The study of chromosomes involves several disciplines, not only because they are essential to hereditary mechanism, but also because these studies allow inferences to be made about numerous aspects of the biology, reproduction, phylogeny and evolution of organisms. An increasingly applied line of research, known as “integrative taxonomy”, uses morphological characters plus a combination of disciplines such as molecular genetics, ecology, cytogenetics, behaviour and biogeography, among others. With the exception of the subfamily Martialinae, cytogenetic information exists for species in all subfamilies of Neotropical ants. This information is distributed unevenly, both in taxonomic groups and geographically, and is patchily concentrated in certain states of Brazil. In this chapter, we review the knowledge on cytogenetics of Neotropical ants, the main techniques used in cytogenetic studies and the analytical models used for inferring karyotype evolution among ants. We also discuss some questions, such as the reproductive models of Hymenoptera, constancy of genome size in ants, and the occurrence of diploid males, and we formulate hypotheses on karyotype evolution in the Formicidae.
... In ants from the Neotropical region, the reports of 18S or 45S physical location are available for 25 species (Mariano et al., 2008;Aguiar et al., 2011;Santos et al., 2010Santos et al., , 2016Barros et al., 2012Barros et al., , 2015Barros et al., , 2016Teixeira et al., 2017;Aguiar et al., 2017). The majority of these species present the GC-rich regions coinciding with the nucleolus organizer regions (NORs). ...
Over the past several decades, ant cytogenetic studies have focused on chromosome
number and morphology; however, recently, additional information concerning
heterochromatin composition and 45S rDNA location has become accessible. The
fungus-growing ants are a peculiar ant group that cultivates fungus for food, and
Trachymyrmex is suspected to be the sister group of leafcutter ants. Cytogenetic
data are so far available for sixn Trachymyrmex species. The present study aimed
to increase the knowledge about Trachymyrmex cytogenetics by the chromosomal
characterization of Trachymyrmex holmgreni including the karyotyping, fluorochromes
staining, 18S rDNA, and microsatellite (GA)15 fluorescence in situ hybridization (FISH).
Karyotyped samples from four ant colonies showed 2n = 20 metacentric chromosomes.
Centromeric heterochromatin rich in GC base pairs was detected in all chromosomes.
FISH revealed the presence of rDNA clusters on the fourth chromosome pair, and
an intense spreading of the microsatellite (GA)15 including exclusively euchromatic
areas of the chromosomes. The GC-rich heterochromatin observed in different ant
species may have a common origin and, thus, phylogenetic implication that needs to
be further investigated. To the best of our knowledge, this study is the first report of
the use of chromosomal physical location of repetitive DNA sequences by means of
microsatellite probes in Formicidae.
... Cytogenetics has also contributed signifi cantly to the resolution of taxonomic problems and phylogenetic relationships in several insect orders (Dincă et al. 2011, Gokhman 2011. Previous such studies on ants have helped to distinguish species groups of controversial taxonomy (Crosland and Crozier 1986, Mariano et al. 2006, Santos et al. 2010, Cristiano et al. 2013). In the tribe Ponerini, substantial variation in karyotype has been documented, ranging from a few metacentric large chromosomes in Pseudoponera stigma (Fabricius, 1804) (Hymenoptera: Formicidae) and Neoponera unidentata (Mayr, 1862) (2n = 12) ) to a high number of small acrocentric chromosomes in Dinoponera spp. ...
The foetida species complex comprises 13 Neotropical species in the ant genus Neoponera Emery (1901). Neoponera villosa Fabricius (1804) , Neoponera inversa Smith (1858), Neoponera bactronica Fernandes, Oliveira & Delabie (2013), and Neoponera curvinodis (Forel, 1899) have had an ambiguous taxonomic status for more than two decades. In southern Bahia, Brazil, these four species are frequently found in sympatry. Here we used Bayesian Inference and maximum likelihood analyses of COI and 16S mtDNA sequence data and conventional cytogenetic data together with observations on morphology to characterize sympatric populations of N. villosa, N. inversa, N. bactronica, and N. curvinodis. Our results showed marked differences in the karyotype of these ants. Both N. curvinodis and N. inversa have chromosome number of 2n = 30. Their chromosome composition, however, is distinct, which indicates that N. curvinodis is more closely related to N. bactronica. These four species clustered into three distinct groups. The close relationship between N. bactronica and N. curvinodis deserves further investigation since it has not been fully resolved here. Our results confirm that N. inversa, N. villosa, N. bactronica + N. curvinodis indeed represent four distinct taxa within the foetida species complex.
... Molecular cytogenetic studies employing fluorescence in situ hybridization (FISH) have provided a clearer understanding of chromosomal evolution, phylogeny and, taxonomy of the species (Kasahara 2009). Molecular cytogenetic data that have used FISH to physically map the ribosomal genes of the Neotropical ants are scarce, and such data are available for only 15 species (Mariano et al. 2008;Aguiar et al. 2011;Santos et al. 2010Santos et al. , 2016Barros et al. 2012Barros et al. , 2015Barros et al. , 2016. All leafcutter ants for which FISH data are available have showed the presence of only a single pair of chromosomes bearing the 18S (Barros et al. 2015) or 45S (18S + 5.8S + 28S) ribosomal RNA genes (rDNA) (Barros et al. 2016). ...
Leafcutter ants of the Atta and Acromyrmex genera are important plagues in different cultures. Cytogenetic data on chromosome number, morphology, and chromosomal banding pattern are only available for 17 species of leafcutter ants. Molecular cytogenetic data for the detection of ribosomal genes by the FISH technique are scarce, and only 15 Neotropical ant species have been studied. This study aimed to physically map the 18S ribosomal RNA genes (rDNA) of six leafcutter ants belonging to the genera Atta and Acromyrmex using FISH. The results were compared with data on the fluorochrome CMA3 currently available for these species. All analyzed species presented the 18S rDNA on one pair of chromosomes. In Acromyrmex subterraneus molestans and Ac. aspersus, FISH signals were observed in the terminal region of the short arm of the largest subtelocentric pair, while in Atta bisphaerica, A. laevigata, and A. sexdens, FISH signals were observed in the interstitial region of the long arm of the fourth metacentric pair. In Acromyrmex striatus, 18S rDNA was located in the interstitial region of the second metacentric pair. The karyotypic formula for Ac. aspersus was 2n = 38 (8m + 10sm + 16st + 4a), representing the first report in this species. The observed 18S rDNA regions in A. laevigata, A. sexdens, A. bisphaerica, Ac. aspersus, and Ac. subterraneus molestans corresponded to the CMA3(+) bands, while in Ac. striatus, several GC-rich bands and one pair of 18S rDNA bands were observed. No differential bands were visible using the DAPI fluorochrome. Karyotype uniformity with previously studied Atta spp. was also observed at the level of molecular cytogenetics using 18S rDNA FISH. A difference in the size of the chromosomal pair carrying the 18S rDNA gene was observed in Ac. striatus (2n = 22) and Atta spp. (2n = 22) highlighting the dissimilarity between these species. The results from the present study contribute to the description of 18S rDNA clusters in Neotropical ants.
... Chromosome number and morphology have been the characters most commonly used in comparative cytogenetic studies of ants, especially among closely related species that are difficult to distinguish based on morphological characters (Mariano et al. 2012). However, other cytogenetic methods have been used recently, such as CMA 3 /DAPI fluorochrome staining in Dinoponera lucida Kempf (Mariano et al. 2008), Wasmannia auropunctata (Roger) (Souza et al. 2011), Odontomachus Latreille, Anochetus Mayr (Santos et al. 2010), Mycocepurus goeldii (Forel) (Barros et al. 2010), and Acromyrmex striatus (Roger) (Cristiano et al. 2013). To aid in distinguishing P. stigma and P. gilberti, we characterized the chromosomes by conventional cytogenetic technique and CMA 3 /DAPI fluorochrome staining. ...
... The CMA 3 + /DAPI − markings aided in characterizing the karyotypes and distinguishing between the 2 species. The distinct CMA 3 + /DAPI − sites, which are chromosomal segments rich in GC base pairs, in the karyotypes of P. gilberti (1st pair) and P. stigma (4th pair) may correspond to their Nucleolus Organizer Regions, as observed in other insects (Manicardi et al. 1996;Kuznetsova et al. 2001;Grozeva et al. 2004;Almeida et al. 2006;Santos et al. 2010). This correlation, however, must be further confirmed with the Nucleolus Organizer Regions banding technique. ...
Pseudoponera stigma (F.) and Pseudoponera gilberti (Kempf) (Hymenoptera: Formicidae) are closely related Neotropical ants, often misidentified due to their morphological similarities. These species also share behavioral and ecological characters. In this study, we examined cytogenetic approaches as a tool to aid identification of P. stigma and P. gilberti. Both numerical and morphological karyotypic variations were identified based on different cytogenetic techniques. The karyotype formula of P. stigma, 2K = 10M + 4SM differs from that of P. gilberti, 2K = 10M + 2SM, and the CMA3 +/DAPI- sites also differ, allowing both species to be distinguished by chromosomal characters.
... A preliminary unpublished molecular phylogeny of the two genera was unable to distinguish between a scenario where both genera are reciprocally monophyletic, and a scenario where Odontomachus is paraphyletic with respect to Anochetus (Schmidt, 2009). Contrasting with those results, morphological and karyotype data have suggested that Anochetus is paraphyletic with respect to Odontomachus (Brown, 1976;Santos et al., 2010). Additionally, several multi-gene phylogenetic analyses focusing on ant genus relationships each recovered four different sister groups to the Odontomachus + Anochetus clade (Brady et al., 2006;Moreau et al., 2006;Spagna et al., 2008;Keller, 2011;Moreau and Bell, 2013). ...
Ants in the genera Anochetus and Odontomachus belong to one of the largest clades in the subfamily Ponerinae, and are one of four lineages of ants possessing spring-loaded “trap-jaws.” Here we present results from the first global species-level molecular phylogenetic analysis of these trap-jaw ants, reconstructed from one mitochondrial, one ribosomal RNA, and three nuclear protein-coding genes. Bayesian and likelihood analyses strongly support reciprocal monophyly for the genera Anochetus and Odontomachus. Additionally, we found strong support for seven trap-jaw ant clades (four in Anochetus and three in Odontomachus) mostly concordant with geographic distribution. Ambiguity remains concerning the closest living non-trap-jaw ant relative of the Anochetus+Odontomachus clade, but Bayes factor hypothesis testing strongly suggests that trap-jaw ants evolved from a short mandible ancestor. Ponerine trap-jaw ants originated in the early Eocene (52.5 Mya) in either South America or Southeast Asia, where they have radiated rapidly in the last 30 million years, and subsequently dispersed multiple times to Africa and Australia. These results will guide future taxonomic work on the group and act as a phylogenetic framework to study the macroevolution of extreme ant mouthpart specialization.
